The present invention relates to an optical disc apparatus. As an example, the present invention relates to a method for spherical aberration correction and tilt correction in an optical disc apparatus.
There are documents described below as documents concerning the spherical aberration correction in the optical disc apparatus.
For example, in Abstract in JP-A-2007-157750, there is a description “in a multilayer optical disc including at least a first recording layer and a second recording layer” “a change of a correction quantity of spherical aberration from a value suitable for the first recording layer to a predetermined value is started before movement from the first recording layer to the second layer is completed.”
For example, in Abstract in JP-A-2006-139841, there is a description “if an attached optical disc is in an unrecorded state, the spherical aberration correction quantity and the focus offset quantity of an object lens are adjusted on the basis of a push-pull signal and predetermined data is recorded on the optical disc. In addition, the spherical aberration correction quantity in a spherical aberration correction element in an optical pickup and a focus offset quantity of the object lens are adjusted on the basis of a reproduced signal obtained from the recorded predetermined data.”
For example, in Abstract in JP-A-2007-164927, there is a description “an object lens 26 is displaced continuously from a lower limit position in a displaceable range toward an upper limit position according to an object lens movement signal. Distances D1, D2 and D3 between a surface L0 of a cover layer and respective recording layers L1, L2 and L3 are calculated by using a focus error signal at the time of displacement of the object lens 26. Spherical aberration correction quantities R1, R2 and R3 respectively associated with distances D1, D2 and D3 are stored.”
For example, in Abstract in JP-A-2003-346369, there is a description “if a disc is a CD/DVD-ROM or a recorded CD-R/RW or DVD-R/RW, jitter is measured intermittently and tilt correction of an object lens is conducted. If the disc is an unrecorded or a partially recorded CD-R/RW or DVD-R/RW, a warp of the disc is detected from a push-pull error signal and a wobbling signal to conduct tilt correction of an object lens.”